Current treatments for viral diseases usually involve administration of compounds that inhibit viral DNA synthesis. Current treatments for AIDS (Dagani, Chem. Eng. News, Nov. 23, 1987 pp. 41-49) involve administration of agents such as 2',3'-dideoxycytidine, trisodium phosphonoformate, ammonium 21-tungsto-9-antimoniate, 1-b-D-ribofuranoxyl-1,2,4-triazole-3-carboxamide, 3'-azido-3'-deoxythymidine (AZT), and adriamycin that inhibit viral DNA synthesis; compounds such as AL-721 and polymannoacetate which may prevent HIV from penetrating the host cell; and compounds which treat the opportunistic infections caused by the immunosupression resulting from HIV infection. None of the current AIDS treatments have proven to be totally effective in treating and/or reversing the disease. In addition, many of the compounds currently used to treat AIDS cause adverse side effects including low platelet count, renal toxicity, and bone marrow cytopenia.
Proteases are enzymes which cleave proteins at specific peptide bonds. Many biological functions are controlled or mediated by proteases and their complementary protease inhibitors. For example, the protease renin cleaves the peptide angiotensinogen to produce the peptide angiotensin I. Angiotensin I is further cleaved by the protease angiotensin converting enzyme (ACE) to form the hypotensive peptide angiotensin II. Inhibitors of renin and ACE are known to reduce high blood pressure in vivo. However, no therapeutically useful renin protease inhibitors have been developed, due to problems of oral availability and in vivo stability.
The genomes of retroviruses encode a protease that is responsible for the proteolytic processing of one or more polyprotein precursors such as the pol and gag gene products. See Wellink, Arch. Virol. 98 1 (1988). Retroviral proteases most commonly process the gag precursor into the core proteins, and also process the pol precursor into reverse transcriptase and retroviral protease.
The correct processing of the precursor polyproteins by the retroviral protease is necessary for the assembly of the infectious virions. It has been shown that in vitro mutagenesis that produces protease-defective virus leads to the production of immature core forms which lack infectivity. See Crawford et al., J. Virol. 53 899 (1985); Katoh et al., Virology 145 280 (1985). Therefore, retroviral protease inhibition provides an attractive target for antiviral therapy. See Mitsuya, Nature 325 775 (1987).
Moore, Biochem. Biophys. Res. Commun., 159 420 (1989) discloses peptidyl inhibitors of HIV protease. Erickson, European Patent Application No. WO 89/10752 discloses derivatives of peptides which are inhibitors of HIV protease.
U.S. Pat. No. 4,652,552 discloses methyl ketone derivatives of tetrapeptides as inhibitors of viral proteases. U.S. Pat. No. 4,644,055 discloses halomethyl derivatives of peptides as inhibitors of viral proteases. European Patent Application No. WO 87/07836 discloses L-glutamic acid gamma-monohydroxamate as an antiviral agent.
Japanese Patent Number 02306992 and Kimura, Agric. Biol. Chem., 53, 1811 (1989) describe compounds of the formula: ##STR1## wherein R is a fatty acid. These compounds were isolated from streptomyces and shown to be useful as peptidoglycan inhibitors.
French Patent Number 2396002 describes quaternary amines, of the formula shown below, which are useful as vasodilators: ##STR2## wherein R.sup.1 is hydrogen or ester and R.sup.2 is C.sub.1 -C.sub.2 alkyl.
The ability to inhibit a viral protease provides a method for blocking viral replication and therefore a treatment for viral diseases, such as AIDS, that may have fewer side effects, be more efficacious, and be less prone to drug resistance when compared to current treatments.
The topic of the present invention is substituted caprolactams and derivatives thereof, which compounds are capable of inhibiting HIV protease and are, therefore, useful for combating HIV diseases, such as AIDS. The caprolactams and derivatives thereof of this invention provide significant improvements over protease inhibitors that are known in the art. A large number of compounds have been reported to be inhibitors of proteases, such as renin, but these have suffered from lack of adequate bioavailability and are thus not useful as therapeutic agents, particularly if oral administration is desired. This poor activity has been ascribed to the relatively high molecular weight of most protease inhibitors, to inadequate solubility properties, and to the presence of a number of peptide bonds, which are vulnerable to cleavage by mammalian proteases in vivo and which generally cause the molecules to be extensively bound in human serum. The substituted caprolactams and derivatives thereof of the present invention and described herein have a distinct advantage in this regard, in that they do not contain peptide bonds, are of low molecular weight, and can be hydrophilic yet still inhibit the viral protease enzyme.
The structures disclosed also have a particular advantage in the presence of a basic amine in the ring; which provides good in vitro potency and aids in formulation, in vivo absorption and CNS penetration of the compound.
The substituted caprolactams of the present invention are particularly useful as inhibitors of HIV protease and similar retroviral proteases.
The compounds of the invention are of low molecular weight and may, therefore, have good oral absorption properties in mammals.